Digital camera, imaging device and method for digital imaging

ABSTRACT

The invention relates to a digital camera, an imaging device and a method for dental digital imaging. One sensor is used for tomographic imaging and at least one sensor is used for transillumination imaging. The sensors are arranged to overlap each other. This arrangement provides a multiple use and a relative inexpensive camera compared with the ones using one sensor with a large area. Additionally, it is possible to arrange at least two separate electric connection structures for the different imaging modes. Further, its connection arrangements can be arranged in such a way that the mechanical connection structures of the camera are separated from the electrical connection structures.

[0001] This invention relates to a digital camera according to thepreamble of claim 1, to an imaging device according to the preamble ofclaim 23, and to a method according to the preamble of claim 38 fordigital imaging.

[0002] In particular, one of the objectives of the invention relates todental panoramic and other tomographic imaging, and to a digital cameraand imaging device used in cephalometric imaging, in which the areacovered by means for receiving the image information is essentiallysmaller than the projection of the object to be imaged on theimage-forming surface. In this context, the image-forming surfacedenotes the virtual plane or surface on which the projection of theobject to be imaged is formed.

[0003] Further, the invention relates to a method for digital imaging inwhich method the object to be imaged is radiated and the radiation isdetected by means for receiving the image information, the area coveredby which being essentially smaller than the projection of the object tobe imaged on the image-forming surface.

[0004] Various tomographic and transillumination imaging methods areused in many kinds of applications. Among others, in the medical andbiotechnological imaging applications, it is typical to direct x-ray,gamma, or beta radiation through the object to be imaged and further tothe image-forming surface. Digital imaging methods have been developedat the side of the traditional film-based imaging methods, and in thesemethods semiconductor sensors, such as CDD sensors (Charge-CoupledDevice) or CMOS sensors (Complementary Metal-Oxide Semiconductor) areused as image-forming surfaces. Typically, in such semiconductorsensors, x-rays are first converted to radiation the wave-length ofwhich is in the region of visible light but the developing technology isalso introducing sensors in which x-rays can be directly converted toelectric form.

[0005] Despite the many advantages offered by the digital imagingdevices, they have not become as generalised as expected in so manyvisions. The prices of digital cameras have been one of the essentialfactors having had influence on this. The semiconductor sensors used inthe cameras are typically made of silicon and, along with the growth ofthe size of the sensor, its manufacturing costs per surface area growexponentially. This is why, in the applications requiring a wide imagingsurface, cameras comprising of one semiconductor sensor will become veryexpensive.

[0006] The invention presented in this application has been developed inview of the needs of dental x-ray imaging, and thus, it will beillustrated below primarily in the light of the applications of thisfield. Naturally, the invention is also suitable for use in connectionwith many other imaging forms.

[0007] The dental x-ray imaging is divided in three main sections, outof which in the so-called intraoral imaging it is typical to imageindividual, or a few teeth, in the so-called panoramic imaging thedental arch is imaged to a plane as a layer, i.e. as a tomographicimage, and in the so-called skull or cephalometric imaging the skullarea as a whole is imaged as a transillumination image. Further, manydevices used for panoramic imaging are suitable for taking even othercross sectional images of various areas of the dental arch. The presentinvention is particularly suitable for use in connection with thepanoramic and other tomographic imaging forms and with the skullimaging, all of which being typically made by the same imaging device.Particularly in the cephalometric imaging, the need for imageinformation receiving means with large surface area has appearedproblematic from the point-of-view of the commercialisation of thedigital imaging applications. Taking a skull image with a sensor havinga directly matching size with the area to be imaged would require use oftens of times bigger sensors as typically used in panoramic imaging.

[0008] As the dental skull image is a transillumination image it istraditionally taken by using so wide a beam and film that the desiredarea has been able to be imaged as one single shot. On the other hand,in panoramic imaging a tomographic image is typically produced by usinga narrow beam and the area to be imaged is scanned by it, whereby thetomographic effect for imaging the desired anatomic layer is created bycontinuously changing the entry angle of the beam in relation to theobject as the beam travels over the area to be imaged. In this so-callednarrow beam tomography method, the movement of the imaging means (theradiation source and the image information receiver) is implemented in acontrolled way so that the receiver is moving in relation to the beamwith a transversal speed corresponding the vertical scanning speed ofthe beam in the area to be imaged, multiplied with a magnifying factor,i.e. a coefficient that is the relation between the distance from theimage information receiver of the focus of the beam (=radiation source)and the distance from the area to be imaged. In this definition, thedetector primarily refers to the radiographic film, whereby, in thedigital imaging, the movement of the image information receiver inrelation to the anatomic layer to be imaged can be replaced by asuitable electric function, as a charge transfer on the surface of thesemiconductor sensor. Mathematically, this imaging equation can bepresented in the following form:

V _(F)=(L _(FF) /L _(OF))×V _(O)

[0009] where V_(F)=speed of film transfer, or an electric function bythe sensor corresponding to it, L_(FF)=distance of film or anyrespective element from the focus of the radiation source,L_(OF)=distance of the object to be imaged from the focus of theradiation source and V_(O)=forward speed, parallel to the image-formingsurface, of the beam in the object. Therefore, the precondition to asuccessful panoramic imaging is that, during the imaging, the respectivepositions of the means to receive the image information, of the area tobe imaged, and the radiation source in relation to each other,continuously remain, as precisely as possible, in compliance with thistheoretical imaging equation.

[0010] In the digital panoramic imaging, the scanning movement of thebeam is followed by a narrow sensor from which the image data is readout during the scan. As the panoramic and cephalometric images havetypically been taken by the same x-ray imaging device, it has been anatural idea to use the so-called scanning slot imaging technology alsofor taking the transillumination images of the skull area (e.g. “Directdigital extraoral radiology of the head and neck with a solid-statelinear radiographic detector”, McDavid, W. D. et al., Oral Surg Med OralPathol 1992; 74:811-7). This is how the sensor surface area needed forimaging has been able to get considerably reduced. In some of suchapplications, however, the scan has been implemented in a way causing atleast theoretical errors in the image, i.e. as the beam is positioned tomeet the image information receiver perpendicularly and the scanning ofthe object is carried out by either conveying the object perpendicularlythrough the beam, or by positioning the object in a fixed position andby moving the radiation source and the image information receiver with aparallel synchronized movement past the object. These kinds of imagingmodes do not produce genuine transillumination images but, as a matterof fact, tomographic images where the size of the tomographic effectdepends on the width of the beam used. In addition to this, interpretingof the images obtained in this way is not familiar to the doctors, astheir projection geometry is different in the horizontal and verticaldirections, thus deviating from the traditional geometry of atransillumination x-ray image. From the point-of-view of practicalapplications, use of the same sensor both in the cephalometric andpanoramic imagings would be desirable, among others regarding theadministration of the camera production and the sensor storagesolutions, as the costs of starting the production and, as themanufactured numbers would get larger, the costs per unit, could thus bereduced. In digital panoramic imaging the height of a typically usedsensor is, regarding the cephalometric imaging, however, sufficient onlyin a few special applications, which is why two different sensors haveto be manufactured for the market. Therefore, the scanning slot imagingas such does not provide a solution based on which one could manage withonly one single sensor.

[0011] A feasible possibility as such would be to use a cephalometricimaging sensor in panoramic imaging in such a way that the sensor heightwould be utilized only partly, but even this solution is problematicfrom the commercial point-of-view. The sensor that is sufficiently highfor cephalometric imaging is more expensive than two panoramic sensors,i.e., with today's prices, the camera needed for cephalometric imagingmight cost even more than the rest of the imaging equipment altogether.As typically only about one third of the panoramic devices are providedwith means for cephalometric imaging, regarding this and the pointspresented above, it is very understandable that the digitalcephalometric imaging applications have not become significantly moregeneral.

[0012] Use of the same digital camera for panoramic and cephalometricimagings has been considered e.g. in the U.S. Pat. No. 5,579,366. Thispublication primarily discusses one dimensional digital cameras, to theevident idea of using a sensor that is high enough even forcephalometric imaging applications, i.e. a camera that is expensive andoverdimensioned from the point-of-view of the needs of mere panoramicimaging. In the scanning cephalometric imaging, a longer sensor than inthe panoramic imaging is needed, in any case, whether the imaging scanis made horizontally or vertically.

[0013] The actual invention according to the said U.S. PatentPublication concerns the camera interface arrangements that seem to beeasy to use as such but that also include potential sources forproblems. Use of the same camera in different imaging positions requiresits repeated transfer between the panoramic and the cephalometricimaging stations and these measures will always imply a risk of damagingthe expensive camera, e.g. as a consequence of dropping it. Oftenrepeated removals and attachments set requirements of their own also tothe mechanical, and particularly to the electric interface solutions ofthe camera. In practice, the problem of the interface solution accordingto the the publication might prove to be the precise and steadypositioning of the camera in the imaging device, which is critical, inparticular, in scanning slot imaging.

[0014] Also in connection with other imaging applications, differentsolutions have been developed to solve the surface area/price problem ofthe semiconductor sensors. Typically in these solutions, sensorscovering only a part of the image-forming surface are used, which arethen moved or transferred during the exposure, or between, individualexposures. E.g. in the mammographic devices different mosaic orchessboard pattern built sensors have been used, which are then movedbetween two or several different exposures. Typically, the differentmodular realisations are expensive and to make them function inpractice, too, the combination of the modules has to be carried out withextreme precision—especially when the intention by combining them is toconstruct a uniform sensor surface based on modules.

[0015] The Patent Publication WO 95/12133 presents a modular sensorarrangement, based on the formation of a kind of zig-zag pattern, to beused in different radiographic and tomographic imaging applications.This as such technically excellent solution has not, however, been shownto become a commercial success, at least not in connection with medicalimaging—probably at least partly due to the fact that, e.g. a uniformpanoramic image cannot be achieved by this kind of a sensor. In thesensor arrangement according to the Publication, the sensor modules areall the time moving, in the direction of the scanning movement, indifferent stages, i.e. in relation to the rotational centre they are ineach moment of time in different positions and are continuously imagingthe object from different projections, i.e. they form images based ondifferent imaging geometries. Therefore, such a sensor arrangementcreates an image formed of stripes of the different projections,parallel with the scanning movement, where on the borders of them theremay be points of incontinuency. In particular, in the (dental) medicalradiographic imaging, these kinds of faults in images are notacceptable.

[0016] Therefore, the objective of this invention is to develop digitalimaging technology to reduce the problems presented above. Inparticular, the objective is to develop a camera that is relativelyinexpensive to manufacture and to acquire, suitable for scanning slotimaging, an imaging device for the use of this kind of camera, and animaging method based on a corresponding technology. In this way, theinvestments to digital technology, become more justifiable and thethreshold for its introduction lower. The digital technology, amongother, will make the doctor's work easier as it enables getting imagesof better quality, and thus more precise diagnoses, but even saving thepictures and administration of them in electric form together with therest of the documentation concerning the patients and the adminstrationof the reception.

[0017] One of the objectives of the invention is to provide such acamera that it can be used in more than one form of imaging,particularly in both tomographic and transillumination imagings,especially in the same imaging device, and possibly in its differentimaging positions. Further, the objective of the invention also is toprovide such a method for digital imaging according to which the samecamera can be used to take both tomographic images and transilluminationimages—even of objects of different sizes.

[0018] Further, one of the objectives of the invention is to provide acamera the sensor surface of which could simply and with moderate costbe modified, implying that one of the objectives of the invention is toprovide this kind of a camera using a modular sensor arrangement. One ofthe additional objectives of the invention is to provide a modularsensor arrangement for the camera in such a way that the characteristicsof the camera can be easily changed, without the need to change itsbasic structure, when one further additional objective of the inventionis to provide the modular sensor arrangement for the camera so that itwill be easy to add modules to the camera in order to increase thesensor surface of the camera, or so that the way it is used can bealtered so that different imaging modes and imaging of objects ofdifferent sizes will be possible with the same camera.

[0019] A particular objective of the invention is to provide such acamera suitable for dental panoramic and other tomographic imaging, thatcan be used, or that can be relatively easily and economically bemodified so that it will also be suitable for dental cephalometricimaging.

[0020] Further, one of the objectives of the invention is to provide amodular sensor arrangement for the camera so that the camera can be usedutilizing only a part of it, especially in tomographic imaging utilizingonly one module, that of the sensor arrangement.

[0021] One of the additional objectives of the invention also is toimplement the sensor arrangement so that the possibly broken individualsensor module could easily be replaceable by a new one, possibly by amodule that is identical with the other modules.

[0022] A further additional objective of the invention is to providesuch a modular sensor system for the camera that the sensor surfaces ofthe modules and/or the circuit boards belonging to the modules can bepositioned also on different levels.

[0023] One of the special objectives of the invention is to provide animaging device in which the same camera according to invention can beused for both tomographic and transillumination imaging, in particular,for both dental panoramic and cephalometric imaging.

[0024] Further, one of the additional objectives of the invention is toprovide such an imaging device whereby a camera according to theinvention can easily and safely be moved from one imaging station toanother and positioned precisely in its correct imaging position.

[0025] Further, one of the additional objectives of the invention is toimplement the camera connection arrangement so that it will consist ofat least two structurally different connectors, to connect the cameracorrectly to its imaging stations for at least two different imagingpurposes.

[0026] Further, one of the additional objectives of the invention is toprovide such an imaging device in the imaging positions of which,designed for at least two different imaging purposes, there arestructurally different connecting arrangements for connecting the camerato the imaging device.

[0027] Further, one of the additional objectives of the invention is toutilize the connection arrangements of the camera to direct the imageinformation received from certain modules of the camera out from thecamera via signal paths exclusively assigned to these modules—inparticular, to direct the image information from one module fortomographic imaging out from the camera via a connection arrangementexclusively suitable for a tomographic imaging station.

[0028] One of the additional objectives of the invention is to realizethe usability of the camera in more than one point of use so that theremoval and connection of it would include as few risks as possible fordamaging the camera itself, as well as its connecting structures.

[0029] Further, one of the additional objectives of the invention is torealize the connecting arrangement of the camera so that its electricconnecting parts would be as little vulnerable as possible to mechanicalstress that might, in time, damage them and lead to intermittent powercontact failures, or even to a permanent failure.

[0030] Further, one of the additional objectives of the invention is torealize the connection arrangement of the camera so that it can bepositioned to its imaging station relatively simply but in the same timeas precisely and for being as non-movable as possible.

[0031] Further, one of the additional objectives of the invention is torealize the connection arrangement of the camera so that it will ensurea stable and safe mounting of it in the imaging device, in order tominimize the electrical safety risks that could be caused by e.g.unusually strong external forces upon the camera. These forces can becaused by e.g. stumbling on the camera so that the connection structureswould bend and cause shortcuts and thus potential damages to the imagingdevice and the camera, or even personal injuries as a consequence of anelectric shock.

[0032] Further, one of the additional objectives of the invention is toprovide such an imaging device where the connection arrangementsintended for the camera have been realized by using separate mechanicaland electric connection structures.

[0033] Further, one of the additional objectives of the invention is torealize the connection arrangement so that its mechanical and electricconnection structures have been separated from each other, e.g. placedphysically on different surfaces of the camera housing.

[0034] Further, one of the additional objectives of the invention is torealize the connection arrangement so that fixing of the camera willtake place in a compulsory sequence of—positioning—locking of themechanical connection—electric coupling.

[0035] The essential characteristics of the invention have beenpresented in detail in the attached claims. One of the maincharacteristics of these is a modular sensor arrangement of a digitalcamera that consists of, in view of sensor surfaces or their projectionson a certain plane, in particular, the point projections in relation tothe focus of the radiation source, an overlapping assembly formed by atleast two sensor modules—or of a structure including at least the firstmodule, and with means arranged for connecting at least another modulefunctionally to the structure to provide this kind of an assembly;whereby the first module has been arranged to be used for scanningtomographic imaging, and whereby this said module has been arranged tobe available for scanning transillumination imaging together with atleast another sensor module. In the same way, in the method according tothese characteristics, particularly one module unit of the modularsensor assembly is used for tomographic imaging, whereby this samemodule, together with at least another module belonging to this sensorassembly, is also used for transillumination imaging, whereby imaging ofeven larger areas than the areas that can be imaged by this first modulewill become possible.

[0036] In particular, the overlapping module assembly according to thisinvention means a sensor arrangement whereby the sensor modules havebeen positioned, in relation to each other, in an overlapping positionso that

[0037] considering the sensor surfaces of the sensor modules, or theirprojections on the plane formed by the axles y, z of a right-angled setof coordinates x, y, z,

[0038] whereby a projection here indicates, in particular, the pointprojection which is imaged to said plane via the focus of the radiationsource used in the imaging and the said sensor surface,

[0039] each of them covers a different area on this plane, and that,

[0040] when proceeding in the direction of the axle y,

[0041] the projection, or the said point projection of the sensorsurface, of each subsequent sensor surface placed on the plane formed bythe axles x, z, will cover a different area from the previousprojection,

[0042] and that the projection, or the said point projection of thesensor surface, of each subsequent sensor surface placed on the planeformed by the axles x, y, will meet that of the previousprojection—possibly by at least partially covering the same area.

[0043] The modular structure according to this definition can thereforebe implemented so that, when proceeding in the direction of the axle y,each subsequent projection, on the plane formed by the axles x, z,covers a different area from the previous projection so that the bordersof these areas meet.

[0044] When the camera with the sensor arrangement according to theinvention is positioned in the imaging device using scanning slottechnology according to this invention, the direction of the scanningmovement of the beam is the direction of the axle z of the definitionabove.

[0045] Thus, the sensor assembly can consist of only the first sensormodule used for tomographic imaging and, in addition to this, the means,such as the space required and the means attached to it for connectingat least one another sensor module functionally to this arrangement, inorder to form an overlapping modular structure.

[0046] In the following, the invention will be described in more detail,using its preferred embodiments and referring to the attached figures,out of which

[0047]FIG. 1 shows a typical traditional panoramic and cephalometricimaging device,

[0048]FIG. 2 shows a structure of a camera housings according to theinvention,

[0049] FIGS. 3A-3E show some sensor module arrangements according to theinvention,

[0050]FIG. 4 shows a collimator system according to one preferredembodiment of the invention used to limit the beam of an imaging device,

[0051]FIGS. 5A and 5B show one way according to one preferred embodimentaccording to this invention to connect the camera to the panoramic andcephalometric imaging device, and

[0052]FIG. 6 shows a camera holder-connector structure in an imagingdevice according to one preferred embodiment according to thisinvention.

[0053]FIG. 1 shows one typical, traditional film-based panoramic andcephalometric imaging device comprising a body part 1, another body part2 movably attached to it, with further a suspension arm 3 movablyattached to the second body part 2, at the essentially opposite ends ofwhich the radiation source 4 and the image information receiver 5 usedin panoramic imaging are located. In the device according to FIG. 1,this image information receiver 5 is a film cassette, but it could also,respectively, be a digital camera attached to the suspension arm 3. Inaddition, positioning means for the object to be imaged are alsotypically used in panoramic imaging; their position in FIG. 1 isreferred to by reference number 6. To control the functions of thedevice, it also typically comprises a user interface 7.

[0054] To the device according to FIG. 1 are attached means for takingcephalometric images, when it also comprises another suspension arm 8with positioning means 9 for the object to be imaged in cephalometricimaging attached to it, as well as means 10 for positioning andattaching the image information receiver, which in the device accordingto FIG. 1 is a film cassette.

[0055] In addition, considering the digital application of this kind ofdevice, a panoramic 11 and respectively a cephalometric 12 imagingstation of the camera 5 have been indicated by reference numbers 11 and12 in FIG. 1. These imaging stations will be later referred to inconnection with the embodiments of the invention according to FIGS. 5and 6.

[0056] When using the imaging device shown in FIG. 1, the object to beimaged is positioned either in a desired tomographic imaging position,in the area indicated by reference number 6, between the radiationsource 4 and the image information receiver 5, or in a desiredcephalometric imaging position, by the positioning means 9 used in thecephalometric imaging. In tomographic imaging, a layer of the desiredanatomy is imaged by moving the radiation source 4 and the imageinformation receiver 5 in a controlled way on the essentially oppositesides of the object to be imaged so that at the same time the area to beimaged is scanned by a narrow beam. On the other hand, for cephalometricimaging, the radiation source 4 is positioned to direct the beam towardsthe positioning means 9 used in cephalometric imaging, and furthertowards the image information receiver not shown in FIG. 1. Thetraditional film-based devices have typically had to be constructed sothat the structures that remain between the radiation source 4 and thecephalometric imaging station 12, as the holder structures of thepanoramic film cassette 5, or the like, have had to be moved aside whenthe device has been changed from panoramic imaging mode to cephalometricimaging mode. In particular, in applications using the same digitalcamera 5 this problem can simply be solved by producing such a panoramicimaging station 11 of the camera 5 that removal of the camera 5 issufficient to leave a free path for the beam towards the camera 5 movedto its cephalometric imaging station 12.

[0057]FIG. 2 shows a structure of a camera housings 51 of a digitalcamera 5 according to the invention. In this embodiment of theinvention, respective apertures 53, 53′ matching the form of one of thesensor module arrangements according to the invention have been arrangedto the actual housing part of the camera 5, which is covered by anupholstery surface which is permeable to the radiation used for imaging.In addition, camera 5 comprises means 60 for positioning and mechanicalfixing of the camera 5, to be later shown in more detail in connectionwith FIG. 6, and means 70 for electric connection of the camera, whichmeans can be implemented so that there are separate connecting means inthe camera, on one hand for different imaging modes, and on the otherfor electrical and mechanical connections of the camera to the imagingdevice.

[0058] FIGS. 3A-3E show some of the sensor module arrangements accordingto the invention. In this context, by sensor module is meant anystructure forming an essentially uniform sensor surface. The sensormodule 20 may e.g. have the structure shown in FIG. 3A, of the sensorstructure 21 formed by four CCD microchips, optical fibre 22,scintillating material 23, housing 24 of the sensor structure 21, cover25 and a printed circuit board (PCB) 27, or the like, coupled to thisstructure by electric interface surfaces 26, but it may also consist of,e.g., a single monolithic CCD chip.

[0059] The sensor module arrangement according to the invention may beimplemented in innumerable different ways out of which some have beenshown in FIGS. 3B-3E. These figures show the structure of camera 5 seenfrom the direction of the focus of the radiation source, when theradiation containing image information is directed via the apertures 53,53′ of the camera housing 52, essentially corresponding to the form ofthe sensor module arrangement of camera 5, to the sensor modules 20,20′, 20″, 20′″ that have been placed on the opposite inner wall inrelation to the apertures 53, 53′0 of the camera housing. A right-angledset of coordinates x, y, z according to the definition used above hasbeen added to the FIGS. 3B-3E, where the direction of the axle z is thesame as the direction of the movement of the camera, i.e. the scanningdirection of the beam, when the camera is used for scanning slotimaging.

[0060]FIG. 3B shows the simplest embodiment, consisting of two modules20, 20′, of the sensor module arrangement according to the invention.With a camera 5 consisting of this kind of a structure one is able totake a tomographic image using one module 20, and a largertransillumination image by using also the other sensor module 20′positioned in overlapping relation to the first module 20. Thestripe-forming effect encountered in tomographic imaging, where at anymoment of time during the imaging scan the sensors are at differentstages, can be controlled without problems in transillumination imaging.When the focus of the radiation source and the object to be imaged areheld stationary and the scanning movement of the beam is implemented bycollimators limiting the beam, the modules moving synchronized with thescanning movement form a true transillumination image, each of them at acertain stage of the scanning movement, i.e. e.g. when using the sensorarrangement according to FIG. 3B, when the modules pass the object fromleft to right, the upper part of the transillumination image will becompleted later than the lower one. Even a long distance between themodules 20, 20′ in the direction of scanning movement is not problematicfrom the point-of-view of the formation of the final integrated imagebut, naturally, e.g. due to the possibly uneven radiation output of theradiation source 4, or regarding the physical dimensions of the camera,this distance should, however, be left as short as will be reasonable,regarding the other solutions of the camera arrangement. And, as in allslot imaging applications of this type, it would also be preferred, inview of the object not to move, to be able to have as short imaging timeas possible, i.e. to keep the distance in between the modules scanningdirection as short as possible for this reason, too.

[0061] If the projections of modules 20, 20′, on the plane formed byaxles x, y at least partly cover the same area this will not cause anyproblems in the formation of a transillumination image, as theoverlapping parts can be integrated by the image processing methodsevident to those professed in the art, to appear as if they had beentaken by one sensor. The partial images can be combined e.g. so that theimage information corresponding to the part of the object that haspossibly been imaged more than once, due to the overlapping of thesensor surfaces, is either removed from the information produced by allthe modules except one, or, in particular, so that all of theinformation received is used in forming the image and the part havingbeen imaged more than once is scaled to correspond the image informationthat would have been received from only one sensor module. On the otherhand, overlapping is also useful regarding the fact that then there willcertainly not be left any gaps between the partial images formed by theseparate modules. In some special imaging modes it may even beappropriate to arrange two ore more modules to image, even totally, thesame area, i.e. to arrange the modules so that, according to thedefinition used above, the projections of the sensors cover the sameareas on the plane formed by the axles x, y.

[0062] According to the invention, the camera 5 may also include three,four, or even more sensor modules to form e.g. an overlapping lineaccording to FIG. 3C, a structure formed by sensor modules of differentsizes according to FIG. 3D, or a structure formed by two columnsaccording to FIG. 3E. Then, FIGS. 3D and 3E illustrate the possibilitythat, according to the definition used above, when proceeding in thedirection of the axle y, the border of the area covered by eachsuccessive projection on the plane formed by the axles x, z can be at adistance in different directions from the border of the area covered bythe previous projection, compared with the previous projection and theone before it, and that these projections may cover, partly or eventotally, the same area. This kind of covering the same area cannot,however, be present when proceeding in the direction of the axle y forany two successive projections.

[0063]FIGS. 3B to 3E only show some simple basic structures that cap becombined and extended in many different ways within the basic idea ofthe invention. Further, according to the invention, the sensor modulearrangement can also be realized e.g. by arranging the modules 20, 20′,20″, 20′″, and, in particular, their surfaces 23 receiving the imageinformation, on different planes, i.e. at different distances from thefocus of the radiation source. This can be realized e.g. by usingconnecting surfaces 26 of different lengths. On the other hand, usingconnecting surfaces of different lengths, it is possible to create astructure where the sensor surfaces are at the same level but where theprinted circuit boards 27, or the like, are at different levels. Thesetypes of arrangements allow more latitude for the implemention of theelectronics arrangements of the camera. The marginal magnification errorcaused by the position of the sensor surfaces at different distancesfrom the objects to be imaged can, if desired, be corrected e.g. by theimage processing methods known as such.

[0064] In order to achieve as effective sensor surface as possible intransillumination imaging using the sensor module arrangement accordingto the invention, it would be preferred to leave the possibleoverlapping portion of the sensor surfaces, naturally even for costreasons, as short as possible. In principle, the sensor modulearrangement could be realized so that, according to the definition usedabove, the projections of the sensor surfaces on the plane formed by theaxles x, y, would not overlap at all, i.e. that the distance betweenthem would be zero. A so precise physical positioning of the modules is,however, technically more difficult to achieve than e.g. an arrangementwhere the modules are positioned at least a little overlapping and thepossible extra overlapping will be taken into account in the imagingprocess, e.g. by using a suitable collimation of the beam. Furthermore,an overlapping of the size of at least one row of sensor pixels ispreferred also because the combination of images is then more easilyfeasible, using means offered by many as such known electronic and/orimage processing software solutions. Especially if the effective heightof the sensor arrangement does not belong to the critical developmentcriteria, the use of overlapping and its optimal magnitude can beconsidered in the light of any particular characteristics of therespective application.

[0065] Regarding the needs of dental imaging, it is preferred to arrangethe module used for tomographic imaging as the lowest module of thesensor module arrangement, as in all other cases especially the imagingof the lower jaw onto the panoramic image is difficult to arrange. Inthese type of applications, it is also preferred to implement the sensormodule arrangement according to the invention so that two identicalmodules, possibly in overlapping positions, are used, and the physicaland electronic arrangements of the camera are implemented so that themodules can be easily removed and/or connected to the camera. Expressedmore precisely, this means that it will be possible, in the first stage,to arrange in the camera housing only the module needed for tomographicimaging, and the physical space needed for the transillluminationimaging module plus the necessary means for its positioning andfunctional connection to the camera. In this way, a panoramic camera isprovided with a relatively inexpensive acquisition price, and to which,however, another module needed for cephalometric imaging can later beconnected in a simple way. In addition to this, thus a damaged modulecan easily be replaced by a new one and if the damaged module happenedto be one used only for cephalometric imaging, the camera can still beused for panoramic imaging purposes even during the time the acquisitionof a new module takes. The price of this type of a panoramic camera canbe made to match the price of a conventional panoramic camera, i.e. thecamera will be significantly cheaper—due to its smaller sensorsurface—than a panoramic camera consisting of one sensor module thatcould as such also be used for cephalometric imaging. In addition, evenprice of a camera according to this invention, extended suitable alsofor cephalometric imaging, consisting of two relatively small sensormodules will, however, remain clearly lower than that of a one modulecamera of comparable size. Even in a more general consideration, asensor arrangement according to the invention can thus be realized sothat, for whatever single module or several modules used only fortransillumination imaging, only the physical space and the necessarymeans for connecting the module functionally to the camera are arrangedto the camera housing, in which case the sensor arrangement can bysimple connection measures be arranged to form a larger overlappingmodular structure.

[0066] According to the invention, there are numerous ways to remove ordiscard the signal produced by other modules than that used fortomographic imaging from the image information used for creating thetomographic image. E.g. the electronics arrangements of the camera canbe implemented so that the signal path to the transillumination imagingmodules can be cut, or so that the image is formed, or the image data istransmitted from the camera to separate image processing means only fromthe signal received from the tomographic imaging sensor. The non-desiredinformation can be sorted out and removed by using electronicsarrangements, known as such, e.g. in the logic circuit of the camera, orlater by image processing methods, known as such. In addition or besidesto these arrangements, it is also possible to proceed so that thecollimation arrangement limiting the beam of the imaging device isimplemented so that, when the imaging device is used for tomographicimaging, the access of radiation to other sensor modules is blocked.

[0067] Further, taking into consideration certain preferred embodimentsto be presented later, one possible solution is to arrange two sets ofseparate electric connection means for the camera, in which case thesignal paths can be arranged so that one connecting element will be inconnection only to the tomographic imaging sensor module and the otherboth to the tomographic imaging sensor module and at least to onetransilluminaton imaging sensor module—or then at least to one of theconnection means arranged for this type of module. Thus, when the firstmentioned electric connector is used for attaching the camera to thetomographic imaging position, automatically, only the image informationproduced by the tomographic image sensor module is obtained via thisconnector, as desired.

[0068] The final formation of the image may be done in ways known assuch, e.g. by connecting the imaging device to a computer, whereby thememory and the processing means of the computer can be utilized. Theprocessing means can also be realized by e.g. a dedicated ASIC circuit(Application Specific Integrated Circuit), connected to memory means,e.g. RAM memory. Naturally, and as already partially described above,many measures of the image information processing can already be carriedout in the camera, e.g. specifically in the ASIC circuit arranged to thecamera. The formation of the final image information as such iswell-known technology to those professed in the art, and a more detaileddescription of it is not necessary for the implementation of theinvention. In principle, the camera may be made by arranging all meansrequired for the image formation in the camera itself when it could beconnected directly to the display device.

[0069] In the implementation of the invention, it is possible to utilizethe CCD sensor technology known as such, having shown to be very usefulin e.g. panoramic imaging. On the other hand, one interestingalternative also is the use of a newer technology based on CMOS sensorsand direct detection of radiation, as with them certain advantages canbe obtained as compared to the traditional semiconductor sensors. TheCMOS sensor technology as such enables, due to its so-called parallelbus type data transfer system, a faster transfer of image information,and with sensors based on direct detection an even better resolution isachieved than with the traditional semiconductor sensors, when there areno scintillating and optical fibre structures reflecting light also tonon-desired directions. The sensitivity of the sensors based on directdetection is better, too. The CMOS technology is the most commonlyapplied semiconductor technology and, because of this, the availabilityof CMOS circuits is good and their manufacturing costs are being reducedby the technical development.

[0070] One of the sensor technologies based on direct detection ofradiation has been described in more detail e.g. in the PatentApplication Publications WO 95/33332 and WO 97/20342. It is not possibleto perform a charge transfer function (Time Delay Integration=TDI) withthis type of a sensor, nor is there any simple way to construct such afunction to it. However, this type of a sensor can be used in theseimaging modes by forming the image so that an image of the object isproduced every time the object to be imaged, or the sensor, has movedabout one pixel forward, and by adding these images to each other sothat they are, at the same time, overlapping a corresponding distance inrelation with each other.

[0071]FIG. 4 shows one preferred embodiment of the invention for acollimator arrangement for limiting the beam, which in the situationshown in the figure has been arranged to be ready for use incephalometric imaging. In cephalometric imaging the beam received fromthe radiation source 4 is first limited by a primary collimator 31(collimator opening 31A) placed in the vicinity of the radiation source4, and before the object to be imaged 33 by another collimator 32 placedto a sufficient distance from the focus, which will limit the beam toessentially match the form of the areas 53, 53′ the camera housing,which are permeable to radiation. The scanning movement of the beam isrealized by the movement of the collimators and the camera is movedsynchronized with this movement. If the sizes of the active surfaces 23,23′ of the sensor modules 21 and of the areas 53, 53′ permeable toradiation, especially their overlapping, are arranged to be larger thanthe effective sensor surface 23, 23′ required in the respective imaging,with a suitable limitation of the beam it will be possible to preventthe unnecessary direction of radiation through the object to be imaged33 twice, to the area of the sensor surface not to be utilized in imageformation, and the image information of the area left outside the beamcan be removed before the partial images are combined.

[0072] Panoramic imaging can be realized in a manner known as such bythe structure according to FIG. 4 by positioning the aperture 31B,intended for panoramic imaging, of the primary collimator 31 in theessential vicinity of the radiation source 4 to limit the beam to matchthe conventional beam used in panoramic imaging, i.e. to essentiallymatch the aperture 53 of the camera housing.

[0073] The FIGS. 5A and 5B show one of the preferred ways to attach thecamera 5 according to the invention to the imaging device. In thesolution according the figures, the camera 5 can be considered aspositioned e.g. to its cephalometric imaging station 12 in FIG. 5A andto its panoramic imaging station 11 in FIG. 5B. In FIGS. 5A and 5B arrow41 indicates the entry direction of the x-rays to the camera 5, i.e. thecamera 5 and the connection arrangements 42A, 42B of the imaging devicehave been arranged to be of different structure, so that the camera 5can, on one hand, only be mounted from one direction to thecephalometric imaging station 12, and from the other direction to thepanoramic imaging station 11 (compare with FIG. 1). When the saiddirections have been arranged horizontally according to FIGS. 5A and 5B,moving the camera 5 between the imaging stations 40A, 40B is easy andfast, and at the same time, the danger of dropping the camera 5unintentionally has been minimized. When positioning oneself to the areabetween the panoramic imaging station 11 and the cephalometric imagingstation 11, 12, the camera is easily removable from one imaging stationand attachable to the other imaging station by using a simple horizontalmovement. In this way, that critical time for the risk of damaging thecamera 5 when it is not safely mounted and secured to the imagingdevice, is reduced.

[0074] Technically, the imaging device according to the invention is,naturally, also possible to realize so that the scanning movement of thebeam is made in some other direction than horizontally. Especially, thepanoramic and cephalometric imaging devices according to the inventioncan be made so that the scanning movement of the cephalometric imagingis arranged to be done in vertical direction, whereby the sensor modulearrangement can be implemented in a somewhat shorter form.

[0075]FIG. 6 shows a connection arrangement 60′, 70′ enabling onepreferred embodiment of the invention shown in FIG. 5 to fix the camera5 according to FIG. 2 to the imaging device. The structure shown in FIG.6 may be considered to correspond the panoramic imaging station 11according to FIG. 5B, when e.g. the respective connecting arrangement(60, 70) forming a structural mirror image may be arranged to thecephalometric imaging station 12. The connection arrangement 42Baccording to FIG. 6 consists means 60′ for positioning and mechanicalmounting of the camera 5 and means associated with the electricalcoupling 70′ of the camera. The camera 5 is brought to the imagingstation 11 in the direction of the guiding rails 61, 62 that ensure thecorrect positioning, from the opposite side of their end plate 63. Whenthe guiding rails 61, 62 have penetrated fully into the matching guidinggrooves in the camera 5, the fixing of the camera 5 can be secured byturning the locking means 64 to its locking position over the camerahousing 51. Additionally, the connection arrangement according to FIG. 6can also be made so that the electric connecting means 71, 72 are movedto contact the matching elements in the camera not until the camera hasbeen mechanically locked, e.g. with a perpendicular movement in relationto the direction of the positioning movement of the camera, which isrealized by a pressing element appearing from below of the locking means64. Thus, the sensitive electric means can be protected from mechanicalstresses by this kind of compulsory operating sequence ofpositioning—securing the mechanical connection—electric coupling. Inparticular, this kind of an arrangement enables the realisation of theelectric coupling and its switching off without any gliding movements ofthe connecting means. The connecting arrangement 42B according to FIG. 6does not cause mechanical stresses to the means 70 involved with theelectric coupling of the camera 5 and the imaging device even when thecamera is connected to its operational station. The mechanical stresseson the electric connectors are problematic, especially if the durationof them is long, as the connection elements may bend with time, orotherwise be damaged to the extent that the electric contact starts tofail, or even becomes cut off permanently.

[0076] As already partly described above, in the solution according toFIG. 6 specifically horizontal rails have been used to reduce thepossibility that the expensive camera would slip to the floorunintentionally during its removal and/or mounting. On the other hand,intention in using more than one guide rail, as well as in separatingthe positioning and the actual locking means to elements of their own,is to ensure the correct positioning of the camera, regarding which inslot imaging, in particular in the direction of the width of the narrowbeam, one must especially precise. The solution according to FIG. 6 ofseparating the actual mechanical connection from the electric couplingalso reduces e.g. the imminent danger of shortcuts by unintentionalcrashes to the camera that could lead to a consequence of damaging thecamera, or the imaging device as a whole, or even to fatal danger in theform of an electric shock.

[0077] The connecting arrangements 42A, 42B of the separate imagingstations 11, 12 can be realized as structurally different so that thecamera 5 can be attached to one imaging station 11 only by using aconnection arrangement 60, 70 only compatible with it, and to anotherimaging station 12 by using another connection arrangement. Thus it canbe ensured that the camera 5 will always be connected correctly to eachimaging station 11, 12. At the same time, the operational life time ofthe electric connectors will be increased when the number of times ofcoupling per connector structure is reduced to half, and even if,despite of the above, one connection arrangement would be damaged, thecamera could still be used at least in one of the imaging stationsduring the time the acquisition of a new camera, or in practice, mostlikely new connecting means, will last.

[0078] As a summary, it can be said that, according to the embodiment ofthe invention shown in FIGS. 2, 5, and 6, there are structurallydifferent connection arrangements for the tomographic and for thetransillumination imaging stations, whereby, respectively, there are twostructurally different connection arrangements in the camera, and theseconnection arrangements consist of separate mechanical connectionstructures and electric connector elements arranged as independentlyfunctioning elements, one for connection for tomographic imaging on onehand and the other for transilluminaton imaging connection on the other.The electric coupling means arranged to the imaging devices areconnected to means for moving them in order to move them into contactwith the coupling means located in the camera, and when the mechanicalconnection means are arranged to consist of separate positioning andlocking means for the mechanical connection, the camera according tothis embodiment of the invention can be attached to the imaging deviceby one connection arrangement consisting of two separate connectionstructures only to a certain kind of connection arrangement of theimaging station, and only using a compulsory operating sequence ofpositioning—securing the mechanical connection—electric coupling.

[0079] Although the invention has been described above mainly by usingpanoramic and cephalometric imaging applications as examples, it cannaturally also be used in connection with any other correspondingimaging applications. For example, according to the invention, anyradiation that can be detected by semiconductor sensors can be used.

[0080] The invention is especially useful in the imaging applications ofmedical technology where x-ray or gamma ray radiation is typically used,or in biotechnological applications where beta radiation is typicallyused. Further, the invention can be applied to industrial testing andquality control methods utilizing transillumination.

[0081] For those professed in the art, it is evident that, especiallywith developing technology, the basic idea of the invention isrealizable in many ways, and the embodiments will not be limited by theabove examples, but they can vary within the scope of protection definedin the attached claims.

1. A digital camera, to be used in tomographic imaging, or in bothtomographic and transillumination imaging, for use specifically in thedental so-called panoramic and other tomographic imaging, or in bothpanoramic and cephalometric imaging, whereby the area to be imaged isscanned by a beam, during which imaging scan the means of the camera forreception of the image information are positioned, or are moving, on adesired image-forming surface, the area covered by which imageinformation receiving means being essentially smaller than theprojection of the object to be imaged on the image-forming surface, andwhich means for reception of image information comprise a first sensormodule intended for reception of the image information produced intomographic imaging, charactrized in that additionally at least anothersensor module intended for reception of image information produced intransillumination imaging is placed in the camera to form a sensormodule assembly where the modules, or their projections, especially thepoint projections of the sensor surfaces of the modules in relation tothe radiation source used in the imaging, are overlapping in relation toeach other on the image-forming surface, or that there is a spacearranged in the camera whereto at least another sensor module intendedfor reception of the image information, created in the transilluminationimaging, can be placed to provide this kind of a module assembly,whereby the electronic arrangement of the camera includes a connectionstructure compatible with said other module, or modules, to connetingsaid other module, or modules, functionally to the camera.
 2. A cameraaccording to claim 1, charactrized in that the camera, or the meansrelated to the using the camera, or the means to form the image from theimage information produced by the camera, includes means to form such animage information signal that includes image information receivedexclusively from the first sensor module, and/or means to form such animage that consists of image information exclusively received from thistomographic imaging module.
 3. A camera according to claim 1 or claim 2,charactrized in that the camera, or the means related to it for usingthe camera, or the means to form an image from the image informationproduced by the camera, includes means for using the image informationproduced by the first module by combining it with image informationproduced by another sensor module, in particular, means for reading theimage information produced by at least two sensor modules in anoverlapping position, and for forming a transillumination imagecorresponding the area covered by both of them together.
 4. A cameraaccording to any of the claims 1 to 3, charactrized in that theoverlapping module structure is formed by a sensor arrangement where thesensor modules have been positioned in relation to each other so that,if the sensor surfaces of the sensor modules, or their projections, areconsidered on the plane formed by the axles y, z of a right-angled setof coordinates x, y, z, whereby a projection here indicates, inparticular, the point projection which is imaged to the said plane viathe focus of the radiation source used in the imaging and the saidsensor surface, each of them covers a different area on this plane, andthat, whereby a projection here indicates, in particular, the pointprojection which is imaged to the said plane via the focus of theradiation source used in the imaging and the said sensor surface, whenproceeding in the direction of the axle y, the projection, or the saidpoint projection of the sensor surface, of each subsequent sensorsurface placed on the plane formed by the axles x, z, will cover adifferent area from the previous projection, and that the projection, orthe said point projection of the sensor surface, of each subsequentsensor surface placed on the plane formed by the axles x, y, will meetthat of the previous projection
 5. A camera according to claim 4,charactrized in that the said projections on the plane formed by theaxles x, y coincide with each other to cover, partly or totally, thesame area.
 6. A camera according to claim 4 or claim 5, charactrized inthat the borders of the areas covered by the said projections on theplane formed by the axles x, z are at a distance from each other.
 7. Acamera according to any of the claims 4 to 6, charactrized in that inthe module assembly, when proceeding in the direction of the axle y, theareas covered by the said projections on plane x, z are always locatedin the same direction of the axle z in relation to the area covered bythe preceding projection.
 8. A camera according to any of the claims 4to 6, charactrized in that the module assembly consists of three or moremodules so that at least one projection, on the plane formed by theaxles x, z, at least partially covers the same area as one of the otherprojections.
 9. A camera according to claim 8, charactrized in that thesensor surfaces, or their projections, form a two column assembly to theplane formed by the axles y, z.
 10. A camera according to any of theclaims 1 to 7, charactrized in that the module assembly consists of twomodules.
 11. A camera according to any of the claims 1 to 10,charactrized in that the sensor surfaces of the modules are essentiallyof the same size, or identical, or that the modules themselves areessentially similar, or identical.
 12. A camera according to any of theclaims 1 to 11, charactrized in that the sensor surfaces of the modulesare positioned to be located on the same image-forming surface, or inthe essential vicinity of the same image-forming surface.
 13. A cameraaccording to any of the claims 1 to 12, charactrized in that the firstsensor module to be used in tomographic imaging is the utmost module ofthe module assembly, especially when the camera intended e.g. for dentalx-ray imaging is positioned to its tomographic imaging position, thelowest module of the module assembly.
 14. A camera according to any ofthe claims 1 to 13, charactrized in that the camera includes aconnection arrangement to enable its mechanical and electric connectionto and detachment of a display device, an imaging device and/or an imageprocessing device, as a computer.
 15. A camera according to claim 14,charactrized in that said connection arrangement includes a connector totransmit the mains power, the image data and/or any correspondingvariables along one signal path from and to the tomographic imagingmodule, and another electric connector that has been adapted to transmitcorresponding variables via another, branching signal path from and tothe tomographic imaging module, and from and to at least onetransillumination imaging module.
 16. A camera according to claim 15,charactrized in that said branching signal path includes means, as e.g.an electronic logic circuit, for combining the partial images producedby two or several individual sensor modules to one uniformtransillumination image.
 17. A camera according to any of the claims 14to 16, charactrized in that the mechanical and electric connection meansof said connection arrangement have been separated to connectionstructures of their own, as by placing said electric connectionstructure to a different side of the camera housing, or the like,surrounding the sensor module arrangement, than its mechanicalconnection means.
 18. A camera according to any of the claims 14 to 17,charactrized in that the mechanical connecting means comprise means forpositioning the camera to its correct position before locking of itsmechanical fixing.
 19. A camera according to any of the claims 14 to 18,charactrized in that its electric connection arrangement has beenimplemented so, that the mechanical connecting of the camera to anotherdevice does not directly bring about an electric coupling with theelectric connection means of the other device.
 20. A camera according toany of the claims 14 to 19, charactrized in that the connectionarrangement includes two sets of structurally different connecting meansfor connecting the camera mechanically for tomographic imaging on onehand, and for transillumination imaging on the other.
 21. A cameraaccording to claim 20, charactrized in that said different mechanicalconnection means are located on different physical surfaces of thecamera housing, or the like, surrounding the sensor module arrangement,when camera is one that is intended for dental panoramic andcephalometric imaging, specifically on the opposite sides of the camera.22. A camera according to any of the claims 14 to 21, charactrized inthat the connection arrangement has been implemented as acompulsory-phased system so that the camera can be connected to theimaging device only by following the sequence positioning of thecamera—locking of the mechanical connection—electric coupling.
 23. Animaging device to be used for tomographic imaging, or both fortomographic and transillumination imaging, especially for use in thedental panoramic and other x-ray imaging, which device comprises aradiation source, a collimator structure for limiting the beam receivedfrom the radiation source, a connection arrangement for mounting thecamera and means for positioning the object to be imaged located at atomographic imaging station, and on the other hand at the possibletransillumination imaging station, as well as means for the controlledmovements of the radiation source, the collimation structure, the cameraand/or the object to be imaged during the imaging scan, when the saidcamera has been positioned, or when it can be positioned using saidconnection arrangement, so that the means of the camera for receivingimage information are situated, or that they can be moved along thedesired image-forming surface, whereas the area covered by the means forreceiving image information is essentially smaller than the projectionof the object to be imaged on this image-forming surface, and where themeans for receiving the image information from the said camera comprisea first sensor module intended for reception of the image informationproduced in tomographic imaging, charactrized in that the cameraadditionally comprises at least one other sensor module intended forreception of image information produced by transillumination imaging, toform a sensor module assembly whereby the modules, or their projections,especially the point projections of the sensor surfaces of the modulesin relation to the radiation source used for the imaging, are inoverlapping positions in relation to each other on the plane of theimage-forming surface, or that there is a space arranged in the camerawhere the other sensor module intended for reception of the imageinformation produced in transillumination imaging can be placed tocreate this kind of a module assembly, whereby the electronicsarrangement of the camera comprises a connection structure compatiblewith the said other module, or modules, for connecting the said othermodule, or modules, functionally to the camera.
 24. An imaging deviceaccording to claim 23, charactrized in that the camera, or the meansconnected with it to use the camera, or the means to form the image fromthe image information produced by the camera, comprises means forforming such an image information signal that exclusively includes theimage information received from the said first sensor module and/or themeans to form such an image that exclusively consists of the imageinformation received from this tomographic imaging module.
 25. Animaging device according to claim 23 or 24, charactrized in that thecamera, or the means connected with it for using the camera, or themeans for forming an image from the image information produced by thecamera, comprises means for using the image information produced by thesaid first module, by combining it with the image information producedby some other sensor module, especially means for reading the imageinformation produced by at least two sensor modules in overlappingpositions, and for forming a transillumination image of the area jointlycovered by them.
 26. An imaging device according to any of the claims 23to 25, charactrized in that the said overlapping module structureconsists of a sensor arrangement whereby the sensor modules have beenpositioned in relation to each other in such a way that, in view of thesensor surfaces of the sensor modules, or their projections on the planeformed by the axles y, z of the right-angled set of coordinates x, y,whereby a projection here indicates, in particular, the point projectionwhich is imaged to the said plane via the focus of the radiation sourceused in the imaging and the said sensor surface, each of them covers adifferent area on this plane, and that, when proceeding in the directionof the axle y, the projection, or the said point projection of thesensor surface, of each subsequent sensor surface placed on the planeformed by the axles x, z, will cover a different area from the previousprojection, and that the projection, or the said point projection of thesensor surface, of each subsequent sensor surface placed on the planeformed by the axles x, y, will meet that of the previous projection,whereby the direction of the axle z corresponds to the direction of thescanning movement used in the imaging.
 27. An imaging device accordingto any of the claims 23 to 26, charactrized in that when the camera ispositioned to its tomographic imaging station, the said first sensormodule to be used for tomographic imaging is the lowest module of themodule assembly.
 28. An imaging device according to any of the claims 23to 27, charactrized in that the collimator structure of the imagingdevice has been arranged to enable the limitation of the beamexclusively to the first sensor module to be used in said tomographicimaging.
 29. An imaging device according to any of the claims 23 to 28,charactrized in that the imaging device comprises means for taking atransillumination image by carrying out the scanning movement of thebeam by keeping the focus of the radiation source steady and by movingthe collimation arrangement limiting the beam in a synchronized way withthe movements of the camera.
 30. An imaging device according to any ofthe claims 23 to 29, charactrized in that the tomographic imagingstation of the imaging device is arranged essentially nearer to thefocus of the radiation source than the transillumination imagingstation, and that the collimator structure of the imaging devicecomprises a primary collimator structure located in the essentialvicinity of the radiation source, and another collimator structure at aconsiderable distance from the focus of the radiation source, near tothe transillumination imaging station, whereby, as seen from thedirection of the focus of the radiation source, the first collimatorstructure has been positioned to a position preceding the tomographicimaging station, and the other collimator structure to a positionpreceding the transillumination imaging station.
 31. An imaging deviceaccording to any of the claims 23 to 30, charactrized in that thecollimator arrangement of the imaging device has been arranged to enablethe limitation of the beam to essentially match the form and size of thesensor module assembly used for transillumination imaging, as byarranging said second collimator structure to limit the beam toessentially match the overlapping assembly of the sensor surfaces of thesensor modules of the camera.
 32. An imaging device according to any ofthe claims 23 to 31, charactrized in that at least two structurallydifferent connecting arrangements have been arranged in connection withthe various imaging stations of the imaging device, for connecting thecamera in a removable way to its respective imaging stations.
 33. Animaging device according to any of the claims 23 to 32, charactrized inthat at least one of the connection arrangements of the imaging devicecomprises separate electric and mechanical connection means.
 34. Animaging device according to any of the claims 23 to 33, charactrized inthat at least in one of the connection means of the imaging device theelectric coupling has been arranged so that that the contacting means ofthe electric coupling can be moved to a physical contact with theirmatching elements in the camera only after the locking of the mechanicalconnection has been completed.
 35. An imaging device according to any ofthe claims 23 to 34, charactrized in that the mechanical connectingmeans of at least one of the connection arrangements of the imagingdevice comprise separate positioning means and means for locking themechanical connection.
 36. An imaging device according to any of theclaims 23 to 35, charactrized in that at least one connectionarrangement of the imaging device, together with its correspondingelements in the camera, have been arranged so that the mounting of thecamera takes place in a compulsory sequence of positioning—locking ofthe mechanical connection—electric coupling.
 37. An imaging deviceaccording to any of the claims 23 to 36, charactrized in that theconnection arrangements of the imaging device, together with theircorresponding elements in the camera, have been arranged so that thecamera can be positioned from opposite sides, on one hand to one, and onthe other to the other of the imaging stations.
 38. A method for digitalimaging to be used, in particular, in dental x-ray imaging, in whichmethod the area to be imaged is scanned by a beam limited by acollimator structure, or the like, and where the radiation, containingimage information, is detected by a camera, in which the area covered bythe sensor surface of the sensor arrangement of the camera isessentially smaller than the projection of the object to be imaged onthe image-forming surface, in which method the same sensor arrangementis used for taking both tomographic images and transillumination images,charactrized in that at least two sensor modules in overlappingpositions are used in the method so that only the image informationdetected by one module of the sensor module assembly is used for theformation of a tomographic image, and for the formation of atransillumination image the image information detected by this one andat least another module in overlapping position.
 39. A method accordingto claim 38, charactrized in that such image information signals and/orsuch an image is formed from the image information produced by thesensor arrangement that exclusively contains the tomographic imageinformation received from one module, by using the means connected tothe camera, or attached to it, for using the camera, or the means forforming the image from the image information produced by the camera. 40.A method according to claim 39, charactrized in that the imageinformation produced by other than the said one tomographic imagingsensor module is removed from the image to be formed using imageprocessing methods known as such, or from the signal produced by thesensor arrangement itself using electronic arrangements that control itsoperation.
 41. A method according to any of the claims 38 to 40,charactrized in that the transillumination image signal and/or thetransillumination image is formed from the image information produced bythe sensor arrangement, containing both the image information producedby the said first tomographic imaging sensor module and the imageinformation produced by at least one other sensor positioned inoverlapping relation to the first one, by combining the imageinformation produced by these modules using means of or being attachedto the camera, or using means for forming the image of the imageinformation produced by the camera, specifically using means that readthe image information produced by at least two sensor modules inoverlapping relation to each other, and form a transillumination imageof the area they are covering together.
 42. A method according to claim41, charactrized in that the transillumination image is formed byreading the image information produced at different stages of thescanning movement from two sensor modules in an overlapping position,and by combining these partial images to one integrated image, in whichcombining process the image information corresponding the possibly moreoften than once produced part of the object is either removed from theinformation produced by any other than a single module, or specifically,where all image information imaged several times is used for imageformation by scaling this part to correspond the image information thatwould have been obtained from a single sensor module.
 43. A methodaccording to any of the claims 41 or 42, charactrized in that intransilumination imaging the beam is limited before the object so thatthe area covered by its projection—seen from the focus of the radiationsource—on the image-forming surface is for the most as big as thecorresponding projection of the sensor surfaces of the sensor modules onthis plane, whereby the image information of the area of the sensorsurfaces possibly left outside of the projection of the beam is removedfrom the image information before combining the partial images.
 44. Amethod according to any of the claims 38 to 43, charactrized in that aconnection arrangement is provided for the camera, with one electricconnector to transmit at least the mains power and image data along onesignal path to the tomographic imaging sensor module and from themodule, and another electric connector that has been adapted to transmitat least the mains power and image data via the other branching signalpath both to the tomographic imaging module and from the module, and atleast to one transillumination imaging module and from the module,whereby the image information received from only the tomographic imagingsensor is read by connecting the camera to the imaging device, or thelike, via the said first electric connector.
 45. A method according toany of the claims 38 to 44, charactrized in that the image informationis collected by a sensor arrangement, whereby the sensor modules arepositioned in an overlapping arrangement so that, if the sensor surfacesof the sensor modules, or their projections on the plane formed by theaxles y, z of a right-angled set of coordinates x, y, z, whereby aprojection here indicates, in particular, the point projection which isimaged to the said plane via the focus of the radiation source used inthe imaging and the said sensor surface, each of them covers a differentarea on this plane, and that, when proceeding in the direction of theaxle y, the projection, or the said point projection of the sensorsurface, of each subsequent sensor surface placed on the plane formed bythe axles x, z, will cover a different area from the previousprojection, and that the projection, or the said point projection of thesensor surface, of each subsequent sensor surface placed on the planeformed by the axles x, y, will meet that of the previous projectionwhereby the direction of the axle z correspondes to the direction of thescanning movement used in the imaging.
 46. A method according to any ofthe claims 38 to 45, charactrized in that the utmost module of themodule assembly is used for tomographic imaging, and, specifically indental radiographic imaging, the lowest module of the module assembly.47. A method according to any of the claims 38 to 46, charactrized inthat in the tomographic imaging the beam is limited to essentially matcha single tomographic imaging module, and respectively, intransillumination imaging to essentially match an overlapping sensormodule assembly.
 48. A method according to any of the claims 38 to 47,charactrized in that in transillumination the imaging scan of the beamis realized by keeping the focus of the radiation source and the objectto be imaged stationary, and by moving the collimator structure limitingthe beam and the sensor module assembly in a synchronized way.